Untitled - CNR

Marine research at CNRthe central part of the Adriatic Sea.The monitored vessels are pelagic trawlers(volante in Italian) and work all alongthe year with the exception of the boatsfrom Giulianova and San Benedetto, whichchange fishing gear at the end of May anduntil approximately the half of Octoberwork as light attraction purse seines (lamparain Italian). Since August 2003, datafrom about 18000 hauls were collected.The map in Figure 2 shows the routes ofthe hauls monitored from October 2003 toDecember 2007. Even though the monitoredvessels belong to different harbours,working then on different fishing grounds,these fishing areas overlap. Furthermore,considering the fact that the area exploitedby the fishing fleet of one harbour is approximatelythe same for each single vesselbelonging to this fleet, conversely it can beassumed that each single area exploited byone vessel is representative of the fishingground of the entire fleet of the consideredharbour. These two aspects have strong implicationson the standardization of CPUEindex [10].In addition, CPUE can also be defined asa function of different environmental conditionsand the results obtained for thisproject ([10] for a complete description)suggest that oceanographic features candetermine abundance distribution. Especiallyin the area of Giulianova (centralAdriatic Sea), conditions were found to bemore favourable to fish aggregation. Forinstance, areas of convergence could befound here [11, 12], both where the southwardlong shore current encounters the descendingbranch of the Middle Adriaticgyre and in correspondence of the frontalzone which separates the coastal fresh waterfrom off-shore saltier waters. Bottomtopography can also be an important factorin determining areas of strong gradientsuch as shelf break fronts. Such conditionscould contribute to fish aggregation in theGiulianova and San Benedetto areas. Furthermore,the Adriatic Sea is an epicontinentalbasin where the contribution of thePo River run-off, strongly influences boththe physical and ecological features of theenvironment. The importance of the correlationbetween anchovy abundance and recruitmentwith river freshwater outputs wasalready proved in previous studies [13, 14]and river effects were reported to be noteworthyin semi-enclosed basin [1]. Theseaspects can play a crucial role in determiningfish aggregation, especially in thenorthern sector of the Adriatic Sea wherethe Po River outflow strongly influencesthe dynamic and sea water properties [11].4 FOS data setAt the end of each haul, catch data (species,number of boxes and sizes), position data(tracks of the vessel’s course steered duringthe trawling phase for volante or meanposition of the vessel while fishing for lampara),depth of the trawl (in form of pressuredata) and temperature of the water areavailable. All these information are includedin separate files which have to bemerged in order to provide geo and timereferenced catch data associated to depthand temperature. To merge the three differentfiles, an ad hoc database (developedin MS Access®) is used.The merging is done for each volante andlampara haul depth data obtained by TPsallow the selection of the initial and finalcoordinates of the haul. All positions includedin this time interval are selected.Catch data are input by the fishermen in theEL sequentially every fishing day; thus theorder of the hauls and their date allow to1893